1. Technical Field
This invention relates generally to monitoring systems for the railroad industry, and, more particularly, to a method and apparatus for determining a condition of the wheels/brake systems on a passing railroad train.
2. Discussion of the Related Art
FIG. 1 illustrates a portion of a train 10 as known in the art. Train 10 includes a locomotive or the like (not shown) as well as one or more vehicles or cars (hereinafter xe2x80x9ccarsxe2x80x9d) 141, 142, . . . 14n. Each car 14, such as shown for car 141, may include a plurality of trucks, such as trucks 161 and 162. Cars come in many different types, for example, a roadrailer type that comes with one truck per car and brake valve. A car 14 could have as many as ten trucks 16, although typically the number of trucks is two (a plurality in any event). As known, however, trucks generally occur in even numbered pairs. In turn, each truck 16, as shown for trucks 161 and 162, typically includes two or more axle bearing systems (hereinafter xe2x80x9caxlesxe2x80x9d), such as axles 181 and 182 for truck 161, and axles 183 and 184 for truck 162. Again, it should be understood that trucks sometimes includes more than two axles (e.g., three), while in other situations, sometimes only one axle.
In addition, train 10 typically includes a pneumatic braking system, which may include a main air pipe from the locomotive (not shown) from which pressurized air is tapped by and to various brake valves, which is shown for car 141 as a brake valve 20. Brake valve 20 controls the operation of a brake cylinder (not shown) which, as know to those of ordinary skill in the art, controls the actuation of one or more brake shoes 22. Each brake shoe 22 conventionally comprises friction material configured for contact against respective wheels 241, 242, 243 and 244. However, in such a mechanical system as described, certain mechanical problems inevitably arise which, if not attended to, may impair efficient operation of the train. For example, on certain mountain railroad grades, a train may operate downhill using the pneumatic braking system described above to control train speed. Long duration, heavy-tread braking on each railway car can cause wheels to become very hot, to the point of doing actual metal temper damage to the wheels, which may be due to a brake valve malfunction. In view of this situation, and further in view of the interest in improving efficient railway operation, it is known to provide a wayside xe2x80x9chot wheelxe2x80x9d detector to automatically (i.e., no human intervention) sense the temperature of wheels of a passing railroad train and alarm when the wheel temperatures become too great for continued safe operation (i.e., the wheels being overheated but still turning). The art is replete with various approaches for automatically detecting xe2x80x9chot wheels.xe2x80x9d As an adjunct, the art has also provided a variety of automatic detection devices to detect hot internal bearings (xe2x80x9chot boxesxe2x80x9d) on a passing railroad train, as seen by reference to U.S. Pat. No. 3,646,343 issues to Caulier et al. entitled xe2x80x9cMETHOD AND APPARATUS FOR MONITORING HOT BOXES.xe2x80x9d However, neither xe2x80x9chot wheelxe2x80x9d detectors nor xe2x80x9chot boxxe2x80x9d detectors are effective in detecting another problem that may occur in a wheel/brake system on a railway vehicle, namely, the problem of a sliding wheel.
In extreme cases, the wheel/brake system can become locked wherein the wheels slide rather than roll. This condition usually involves empty or light weight cars. Nonetheless, in the foregoing-described case of wheels not retarding properly (i.e., either sliding or malfunctioning), existing xe2x80x9chot wheelxe2x80x9d and xe2x80x9chot boxxe2x80x9d detectors have not measured a high temperature, as they were designed to do. Accordingly, such conventional detectors have not stopped such trains for overheated wheels or bearings. The sliding wheel situation can result in wheels with an out-of-round shape, either from the wheel running-surface metal wearing away (i.e., leaving flat spots) or from metal adhesion tearing away the top surface of the running rails wherein the torn away metal is actually deposited on the wheel running surface. This results in a built-up tread defect. The foregoing-described defects can cause a wheel flange to jump over the rail (i.e., a loss of guide-way), break the rail (i.e., an excessive shock force) or break the wheel (i.e., an excessive shock force or loss of metal temper) when the wheel again begins to turn. These conditions can result in a quick, and unexpected derailment.
One approach taken in the art in an effort to detect sliding wheels involves a camera-based system that sought to capture the 2-D temperature profile of a wheel. Such system, however, had a variety of problems, including durability (respecting the camera), complex processing, and in the end, unreliable detection.
There is therefore a need to provide an improved automated system for monitoring a moving train on a track that minimizes or eliminates one or more of the problems as set forth above.
One object of the present invention is to minimize or eliminate one or more of the problems as described in the Background. One advantage of the present invention is that it automatically monitors and detects poorly performing wheel/brake systems, including a sliding wheel condition. The invention recognizes the behavior of a locked or sliding wheel as its temperature is reduced compared to that of other wheels on the same brake system that are being braked normally, due to the large amount of heat generated by the braking action itself (i.e., the friction material in contact with the wheel itself) particularly as compared to a sliding wheel. Thus, unlike the hot wheel or hot box automatic monitoring and detection system known in the art, which look for an increased temperature above a predetermined threshold, the present invention is configured to recognize an abnormally low wheel temperature as a possible malfunctioning wheel/brake system or even a sliding wheel condition.
A method of monitoring a train moving on a track is provided and includes a first step of determining a first temperature parameter of a first wheel of a first axle of the train. A second step includes determining a second temperature parameter of a second wheel of a second axle of the train different from the first axle. Finally, detecting a malfunctioning wheel/brake such as a sliding condition when a ratio between the second temperature parameter and the first temperature parameter exceeds a predetermined threshold. Preferably, the method also includes the step of checking the average temperature to ensure that braking is actually occurring (i.e., that an average temperature exceeds a predetermined limit).
In a preferred embodiment, the method further includes the step of identifying a car in the train, which includes at least the plurality of trucks having brakes under the control of a brake valve. The invention preferably analyzes wheels associated with a particular brake valve together. In the preferred embodiment, the step of determining the first temperature parameter may be performed in relation to the axle being checked for a sliding condition. Preferably, the first temperature parameter is the higher one of the measured temperature values of the two wheels on such first axle. The step of determining the second temperature parameter may be performed by the substeps of measuring temperatures for each one of the pair of wheels of each axle of the controlled trucks (i.e., those wheels/axle trucks whose brakes are controlled by the same brake valve) other than the first axle, and producing respective measured temperature values; selecting, on a per axle basis, the lower one of the pair of measured temperature values; and, calculating the second temperature parameter by averaging the lower measured temperature values selected above in the selecting step.
A wheel""s temperature (i.e., the wheel under test) when compared to the average of the temperatures of the other wheels on the same brake group, will develop or otherwise result in a ratio. This process when repeated for each axle within the brake group will result in a set of ratios. When the ratio of any given wheel/brake combination exceeds the above-described predetermined threshold, an alarm is generated.
An apparatus for monitoring a train moving on a track is also presented.
Other objects, features, and advantages of the present invention will become apparatus to one skilled in the art from the following detailed description and accompanying drawings illustrating features of this invention by way of example, but not by way of limitation.